Ring of Liquid Identification

(Created by Craig Stenseth, in Bazaar of the Bizarre, Dragon magazine #82)
This silver ring is worked in wave patterns and has a single clear stone. When brought to within one inch of at least four ounces of liquid, the stone changes color to indicate the liquid's identity. If the liquid does not fall into one of these categories (such as blood or demon ichor), the stone remains clear.
Color/Liquid
Red/Poison or magic potion
Orange/Oil or flammable liquid
Yellow/Contaminated water
Green/Acid or corrosive
Blue/Drinkable water
Indigo/Saltwater
Violet/Alcoholic beverage
White/Holy water
Black/Unholy water